Chondroitin sulfate proteoglycans (CSPG) labeled with antibodies to the glycosaminoglycan (GAG) chains are present in the pathway of thalamic afferents, and are associated with segregation of this pathway above the efferent pathway. These results suggest that CSPGs are permissive to thalamic axons, and are guiding thalamocortical axons to their position in the cortex. These same molecules in tissue culture of dorsal root ganglia cells and retinal explants inhibit axon outgrowth. To directly determine the effects of CSPG on CNS axons, we will return to tissue culture systems. Using both standard neurite outgrowth assay and three dimensional collagen matrix system we will determine if l) The cell type within the CNS, 2) The culture system, 3) Cellular and molecular interactions or 4) The components of CSPG (GAG, core protein or whole molecule) have different effects on neurite outgrowth. We will look at outgrowth from thalamic and cortical neurons and will compare these results to work currently in progress in the sponsor's laboratory with cerebellar granule cells, where CSPG appear inhibitory to axonal outgrowth. The proposed research will attempt to resolve these conflicting finding, and in doing so increase understanding of the molecular mechanisms of axonal pathway formation in the developing CNS. Knowledge of the normal mechanisms of pathway formation is important for both understanding principles of normal brain formation, and also how these could be affected by disease states. These findings may unlock therapeutic manipulation of these in clinical setting such as spinal cord injury or stroke, especially in the developing nervous systems of neonatal and young children.